Reduced coenzyme Q10 is a compound that not only exhibits higher oral absorbability as compared with oxidized coenzyme Q10 but also is very useful as an antioxidant, and it can be produced by reducing oxidized coenzyme Q10 obtained by a conventional method such as synthesis, fermentation, and extraction from a natural product. However, reduced coenzyme Q10 is prone to oxidation into oxidized coenzyme Q10 by molecular oxygen, and therefore a remaining important challenge is to maintain reduced coenzyme Q10 with stability during processing of reduced coenzyme Q10 into a base material or a composition for food, food with nutrient function claims, food for specified health use, nutritional supplement, nutritional product, animal drug, drink, feed, cosmetic, pharmaceutical product, therapeutic drug, prophylactic drug, etc. and/or during storage after the processing.
Various methods aiming improvement in stability or improvement in absorbability of reduced coenzyme Q10 have heretofore been studied.
For example, there is known a method of improving oxidation stability by protecting a hydroxyl group of reduced coenzyme Q10 with an acyl group or an ether group (Patent Document 1).
On the other hand, as to a method for improving absorbability, improvement in hydrophilicity has heretofore been believed to lead to improvement in absorbability because reduced coenzyme Q10 is higher in absorbability than oxidized coenzyme Q10, and there have been reported derivatives with a hydrophilic group such as PEG (polyethylene glycol) having been introduced (Patent Document 2), derivatives with glycine having been introduced (Patent Document 3), and derivatives with succinic acid having been introduced (NON-Patent Document 1).